The present invention relates to an electric apparatus including a gas insulated bus bar and a switch.
A conventional arrangement including gas insulated bus bars and switches is as shown in FIGS. 1 and 2. Denoted by numeral 1 are main bus bars, each including a plurality of bus bar units 2 interconnected by connecting bus bars 3.
Denoted by numeral 4 are line circuit breakers connected to the respective ones of the bus bar units 2 of the main bus bar 1.
Each of the line circuit breakers 4 includes a bus bar disconnecting switch 5, a circuit breaker 6, a line disconnecting switch 7, a grounding device 8 and a cable head 9, which are, together with one of the bus bar units 2, mounted on a base 10 to form a unit corresponding to each line. Each unit including the line circuit breaker 4, the bus bar units 2 and the base is assembled and tested in the factory, and thereafter installed in the designated site. The line circuit breakers 4 are installed in the order of from one end to the other, or from the center towards both sides. Installation must be so made that the bus bar unit 2 of every unit is in alignment with the axis of the main bus bar 1.
Generally, interconnection between the bus bar units of the main bus bar is achieved by tulip contacts and therefore stringent dimensional accuracy is required in the position alignment. Moreover, since the unit including the line circuit breaker 4 is heavy, it must be installed by means of a crane. During the installation, position alignment of the connecting portions is made and also the conductors are moved in a horizontal direction against the contact pressure to achieve engagement. Such operations need to be simultaneously carried out while the line circuit breaker is suspended by a crane and are therefore associated with difficulties and hence require time and labor. Also, to conduct periodical tests during the use of the line circuit breakers for inspecting the bus bar disconnecting switch 5, the circuit breaker 6 has to be separated from the rest of the entire system. Furthermore, to check a bus bar disconnecting switch 5 in the middle of the main bus bar 1, it is necessary to remove the circuit breakers 6 and the bus bar disconnecting switches 5 of all the line circuit breakers situated between the particular bus bar disconnecting switch and either end of the bus bar. Thus, a great amount of work is involved and power transmission is interrupted over a long time.